SRAM

It is time to shift up a gear - SRAM knows that technological progress must prove itself in practice. Especially on a bicycle, which should be easy to use. Elegance means doing without everything superfluous. This is progress, and SRAM's specification for the first electronic circuit, the SRAM Red eTap®.
The eTap® batteries can be removed literally with one click.
Open the closure system without any tools, slide the battery up and out of the rear or front derailleur and plug it into the USB charger. You can connect the charger to any USB-enabled power source or connect it to the mains with an A/C USB adapter.
The charging time is only 45 minutes.